1. Technical Field
This disclosure relates generally to contact image sensors and, more particularly, to a contact image sensor system having one or more staggered rod lens arrays.
2. Background Information
Contact image sensors (also referred to as a “CIS”) are widely used for optically scanning samples due to their relatively low costs. A typical CIS includes a rod lens array having a plurality of cylindrical micro lenses, and a detector array having a plurality of charge-coupled devices (also referred to as a “CCD”). Each micro lens is configured to direct light from a target to be imaged (e.g., a biological sample, which target is referred to hereinafter as a “sample”) to a respective one of the CCDs, producing one pixel of an image of the sample. Collectively, the pixels from each of the CCDs are compiled together to produce the image of the scanned region of the sample.
Typically, the prior art image sensors have a resolution that depends upon the distance between the rod lens array and the sample. For example, to enhance the resolution of the CIS to a sub-micron level, the distance between the rod lens array and the sample must be reduced to a sub-micron level. FIG. 4 illustrates the typical relationship between working distance and resolution in prior art CISs. As can be seen from the graph, there are limitations regarding the resolution that can be attained using prior art CISs. Even in those applications where an acceptable high resolution can be reached, the working distance is such that it is quite difficult to position the sample being imaged.